Flashcards in 23. Acute Diarrhea Deck (117):
Infectious diarrheal disease is the ___ leading cause of death worldwise
____ leading cause of childhood death
What is the time frame for acute diarrhea/
What is the definition for diarrhea?
>200 grams per 24 hour period
3 or more loose/watery stools per day or clear increase in frequency over baseline
When does most diarrhea occur?
Winter months (viral)
WHat is the length of the SI? What is mostly absorbed there?
Macronutrients: carbs, fat, nitrogen **absorbed in the proximal 100 to 150 cm
How much of the 10 L of chyme that under the duodenum exits the SI?
Consequence on pathology in this area?
SI does the bulk of the absorption, therefor pathology is very dramatic there
S/s of infections in the small bowel?
Large volume of watery diarrhea
Abdom cramping, bloating, gas, and weight loss
**fever is rare
**rare stool WBCs/occult blood
S/s of infections in the large bowel?
Frequent, small, regular stools
Painful BM of tenesmus (painful urge to have a BM)
Bloody and mucoid stools
RBCs and WBCs on stool smear
What is the infectious cause of most gastroenteritis?
Viral (cultures only positive in 1.5-5.6 cases
What is the definition of severe, community acquired diarrhea?
>4 fluid stools per day
What are the bacterial agents that commonly cause acute GI illness?
E. coli 0157:H7
What are the viruses that commonly cause acute GI illness?
Adenovirus (40 and 41)
What are the protazoa that commonly cause GI illness?
What are the two viruses that cause colon infection in immunocompromised people?
What are non-infectious causes of diarrhea?
Stool impaction-overflow diarrhea
What happens with osmotic diarrhea?
Neither SI nor colon can maintain an osmotic gradient
Unabsorbed ions in the lumen cause water retention
What SHOULD the intraluminal osmolality be?
What are some things that can cause osmotic diarrhea?
- Ingestion of poorly absorbed ions or sugar alcohols (mannitol, sorbitol, Mg, sulfate, phosphate)
- Disaccharidase deficiency (lactase deficiency)
What causes cessation of osmotic diarrhea?
Cessation of the offending substance
Electrolyte concentrations in stool water with osmotic diarrhea
Low concentrations, because electrolyte absorption is not impaired
What is the problem underlying secretory diarrhea?
- Net secretion of anions (Cl- or bicarbonate)
- Inhibition of net sodium absorbtion
What is the most common cause of secretory diarrhea?
What are three actions of enterotoxins that cause secretory diarrhea?
1. Interact with receptors and modulate intestinal transport
2. Block specific absorbative pathways in addition to stimulating secretion
3. Inhibit Na+/H+ exchange in the SI and colon
How is the osmotic gap calculated?
Gap=Serum Osm - estimated stool Osm (2 x ([Na]+[K]))
What is a normal sized osmotic gap that can result from not being able to count all of the cations?
Under 50 mOsm/kg
What kind of osmotic gap will be present in osmotic diarrhea?
Over 100 mOsm/kg
What causes a negative osmotic gap?
Poorly absorbed multivalent anion like phosphate or sulfate
Why is measured stool osmolality of little value?
Tends to rise once the stool has been collected due to continuing bacterial fermentation in vivo
What kind of laxitive can cause a large osmotic gaP?
What is useful to look at to see if stool samples have been diluted with urine in the case of laxitive injestion?
Stool osmolarity (very high if stool is diluted with urine)
What is the #1 foodbourne illness in the US?
What is salmonella typhi infection assoc with?
Poultry, milk, eggs
People with salmonella typhi infection have increased risk for:
Gallbladder colonization and gallstones
Patients with sickle cell disease have an increased risk for:
Sx of acute salmonella typhi GI infection:
Anorexia, ab pain, bloating, N/V, bloody diarrhea
**Colonic/dysenteric like illness despite small bowel disease
What area of the GI does shigella most commonly infect/
Left colon, ileum might also be involved
What is shigella rarely assoicated with? (3)
What is the leading cause of acute bacterial diarrhea worldwide?
What are three things that can result from Campylobacter jejuni infection?
Reactive arthritis or erythema nodosum
Guillian Barre syndrome
Pseduoappendicitis (bad abdominal pain)
What is the most common pathogenic parasitic infection in humans?
How is giardia lamblia acquired? Presentation?
Drinking unfiltered/rural water
Acute/chronic diarrhea with upper abdominal pain
What are the 4 kinds of E. coli infections?
Enterohemorrhagic (EHEC) 0157:H7
What type of E. coli resembles shigella and produces blood diarrhea?
What type of E. coli attaches to enterocytes via adherence fimbriae
What type of E coli is associated with HUS?
What are the two toxins that Enterotoxigenic E coli has?
Heat-labile: like cholera toxin
Heat-stabile: increased IC cGMP with effects similar to cAMP electations by LT
How does the cholera enterotoxin cause disease?
- Increase in IC cAMP
- Opens CFTR
- Releases Cl- into lumen and water follows
What causes about half of all gastroenteritis outbreaks worldwide
What is the principal cause of traveller's diarrhea?
Enterotoxigenic E coli
Who is most susceptible to rotavirus infection?
Children between 6 and 24 months
What is an extra-GI sx that ascaris (nematode) can cause?
Ascaris pneumonitis (cough)
What causes stronyloides infections to persist?
Autoinfection: Adult worms in the intestines lay eggs that hatch and release larvae that penetrate the mucosa
What is the leading cause of IDA in the developing world?
Hookworms like Necator americanus and Ancylostoma duodenale
What are some parasites that are more likely to infect patients with lymphoma, BMT, HIV?
What are some bacteria that are more likely to infect patients with lymphoma, BMT, HIV?
MAC (myobacterium avium complex)
What are some viruses that are more likely to infect patients with lymphoma, BMT, HIV?
What defines nosocomial diarrhea?
New diarrhea at least 72 hours after admission
**increases the length of stay, severity depends on age
What is the most common cause of nosicomial diarrhea?
**also tube feeds, meds, fecal impaction, ischemic colitis, and CMV/HSV/GVHD in BMT transplants
What does diarrhea within 6 hours of eating suggest?
Ingestion of a toxin--S.aureus in potato salad or Bacillus cereus in Chinese food/rice
What does diarrhea at 8-14 hr after eating suggest?
What is needed for diagnosis of the etiology of infectious colitis?
**endoscopy not indicated
What is a stool culture indicated?
- Severely ill
- Hospitalization requirement
- IC patients
- some employees
Why are there many false negatives for ova and parasites? What must be done because of this?
Ova shed intermittantly
Repeated 3x (3 consecutive days, 24 hr apart)
When should stool for O and P be ordered?
Persistent diarrhea >14 days
Travel to mountainous regions
Exposure to infants in daycare
Community waterborne outbreak
What are ELISAs or DFA good at identifying in the school?
What is the key aspect of treatment for diarrhea?
What are the important factors for oral rehydration in diarrhea tx?
Intestinal glucose absorption via sodium-glucose cotransport remains intact
Intestine able to absorb water if glucose and salt are present
What is the Na/glucose cotransporter on the apical surface?
How does EHEC presentation differ from the other E coli infections?
Why is it important to distinguish between EHEC and the other E. colis?
Don't want to give EHEC antibiotics--precipitates HUS
Presentation and Tx for traveller's diarrhea (enterotoxic E.coli)
>4 stools daily with fever, blood/pus/mucus in stool
Prompt tx with fluoroquinolone or TMP-SMX (reduces duration from 3-5 to 1-2 days)
What are the indications for empiric antibiotics for diarrhea? What antibiotic?
Fever, bloody diarrhea, and the presence of occult blood or fecal leukocytes in the stool
**except for C. diff and EHEC
Fluoroquinolone for 3-5 days (azithromycin and erythromycin if there is resistance)
What are two antimotility agents?
When is the only time that antimotility agents should be used?
If fever is absent and stools are NOT bloody
What happens if you use antimotility agents for EHEC?
Facilitates the development of HUS
Classification of C. diff
Gram + spore forming anaerobic bacteria
Transmission of C. diff?
What % of inpatients have asymptomatic colonization with C diff? Outpatients?
Why do newborns have a high carrier rate but don't get infected?
Don't have the receptors that the toxins bind to, don't get sick
How many days from exposure to sx with c diff?
Of the C. diff spores and vegetative cells ingested, which one makes it to the small bowel?
Spores can survive the stomach acidity and germinate in the small bowel upon exposure to bile acids
Where does C. diff colonize?
What happens after antibiotics destroy normal bacterial flora?
C. difficile grows and secretes toxins
Toxins inflame and ulcerate the mucosa
Damaged mucosa secretes fluid that causes the diarrhea
What are the toxins produced by C. difficile?
Toxin A: potent enterotoxin
Toxin B: cytotoxin in vitro
What C diff toxin is typically tested for?
What are characteristics of the hypervirulent C. diff strain
BI/NAP1/027 strains have 16x more toxin A and 23x more toxin B
tcdC gene mutation may have increased toxin levels
Increased fluoroquinolone resistance
What are the typical clinical feautures of C. diff colitis?
Bloody, watery diarrhea
Leukocytosis (VERY HIGH)
What are the features of severe forms of C. diff infections ?
Important modes of prevention of C. diff?
HAND WASHING (alcohol based gels don't work)
Minimize antibiotic exposure (esp quinolones)
What are the mainstay therapies for primary C. diff?
**similar efficacy, but vanco is slightly more effective for severe cases
Severe C diff disease is defined as any one of the following:
1. Age over 65
2. Creatinine over 1.5 times baseline
3. WBC > 15K
What percent of patients with C. diff will have recurrence of sx after intial infection?
What are risk factors for recurrence of C diff infection?
COntinued antibiotics (prevent reest of normal flora)
Age and comorbidities
What are the options for tx of recurrence of C diff
Repeat initial therapy
Switch to vanco
Vanco taper (allow good bacteria to return)
Rifaximin chaser (follows vanco)
What is an alternative to vanco for C diff that inhibits RNA pol, but lacks activity vs gram negative bacteria, preserving some natural flora?
Fidaxomicin (low serum conc, high fecal concentration)
**has better protection against recurrence than vanco
What are the risks of using probiotics for protecting against C diff recurrence?
Fungemia from sacchromyces
Endocartitis from lactobaccilus and bifidobacteria
**in IC and critically ill patients
What is the probiotic that is MC used following C diff tx?
What antibodies increase following C diff infection?
Anti-toxin A and B antibody levels
**High IgA anti-toxin A is 48x more protective than low levels
What is the MOA of IVIG for C diff?
Neutralization of toxin A thorugh IgG anti-toxin A antibodies
**good choice for patients that are immunosuppressed
What is IBS?
Recurrent and relapsing abdominal pain, bloating, and change in bowel habits including diarrhea and constipation
Causes of IBS
Abnormal GI motility
When does IBS manifest? Labs?
20-40 yo in females
Labs all normal, normal endoscopy
What is the Rome III criteria for IBS?
Recurrent abdominal pain or discomfort 3 days/month in the last 3 months along with 2 or more of the following:
1. Improvement with defecation
2. Onset assoc with change in BM frequency
3. Onset assoc with change in appearance of stool
What happens in diverticular disease?
Pseudodiverticular outpouching of the colonic mucosa and submucosa
Nerves and arterial vasa recta penetrate the inner circular muscle coat to create discontinuities in the muscle wall
Who gets diverticular disease? Under what conditions? Exacerbated by:
Older people (505 in Western adult populations over 60)
Conditions of elevated intraluminal pressure in the sigmoid colon, exacerbated by diets low in fiber which reduces stool bulk
What region of the colon is MC affected by diverticular disease?
Obstruction of diverticula leads to:
What can happen with perforation in diverticulitis?
Sx of diverticular disease?
20%: cramping, lower abdominal discomfort, constipation, diarrhea
What might prevent development of diverticulitis from diverticular disease? Tx if diverticulitis develops?
High fiber diet
Resolves spontaneously or after antibiotic tx
What causes appendicitis in 50-80% of cases?
Overt lumenal obstruction like a stonelike mass of stool (fecolith)
What is the name for the point where abdominal pain focuses in appendicitis?
McBurney's point: right lower quadrant
What is McBurney's sign?
Deep tenderness noted at 2/3 the distance from the umbilicus to the right anterior iliac spine
What causes mucosal infartion ischemic colitis? Transmural infarction?
Hypoperfusion: hypotension or arterial spasm
Arterial occlusion: thrombosis or embolis
What are the two watershed regions that are particularly susceptible to ischemic colitis?
1. Splenic flexure (SMA to IMA)
2. Sigmoid colon and rectum (IMA to pudendal)
What will be seen on endoscopy with ischemic colitis?
Segmental and patchy hemorrhage/ulceration of the mucosa
Who gets ischemic colitis?
Older people with coexisting cardiac or vascular disease